In the practice of diagnostic medicine, it is often necessary or desirable to perform a biopsy, or to sample selected tissue from a living patient for medical evaluation. Cytological and histological studies of the biopsy sample can then be performed as an aid to the diagnosis and treatment of disease. Biopsies can be useful in diagnosing and treating various forms of cancer, as well as other diseases in which a localized area of affected tissue can be identified.
Biopsies are routinely performed on tissue using a needle set. One known needle set includes an elongate outer cannula having a pointed tip and a tissue receiving aperture defined near its distal end, and an inner cannula having an open distal end surrounded by an annular cutting blade. The inner cannula is slidably disposed within the outer cannula so that it can close the tissue receiving aperture, thereby cutting tissue prolapsing into the lumen of the outer cannula through the tissue receiving aperture. Typically, a tubular introducer is disposed around the outer cannula of a needle set. The typical introducer is a tube with an open end through which the outer cannula extends.
Most biopsies are performed with a standard aperture and a standard stroke length (i.e., the travel distance of the inner cannula inside of the outer cannula). For instance, a 20 mm aperture and a corresponding 23 mm stroke length are typical for vacuum assisted breast biopsy procedures. In some instances, the physician may prefer a smaller aperture and/or a shorter stroke length. One such instance is when a compressed breast measures 20 mm or less. In that case, a 20 mm aperture may not fit inside of the compressed breast, and the tissue piercing tip may exit the far side of the breast or impact the underlying rib cage. The physician may prefer to use a 12 mm aperture to ensure that the aperture and the distal tip, which measures 8 mm, will both fit inside of the compressed breast. A smaller aperture is especially important when the biopsy device must be positioned using stereotactic X-ray guidance.
For a reduced size aperture, a corresponding reduced stroke length of 15 mm increases the efficiency of the biopsy device by reducing the stroke time and biopsy time. Further, reducing the stroke length also reduces the distance between the open distal end 28 of the inner cannula 26 and the tissue receiving aperture 20. This reduced distance, in turn, reduces the amount of liquid, introduced through the annular lumen, which exits through the inner cannula lumen 32, instead of the tissue receiving aperture 20. The irrigation system that introduces liquid (e.g., saline) through the annular lumen between the outer and inner cannulas 16, 26 is described in U.S. Provisional Patent Application Ser. No. 62/055,338, filed on Sep. 25, 2014, and assigned to the same assignee as the instant application, the contents of which are incorporated by reference as though fully set forth herein. Moreover, reducing the stroke length also maximizes the overlap between the inner cannula 26 and the introducer 34, thereby maximizing the structural integrity of the portion of the biopsy device 10 in the tissue.
Current breast biopsy procedures include selecting and setting up a tissue biopsy device with an appropriate aperture and stroke length after the breast is compressed and the size of the compressed breast is determined. This delay in the procedure increases the amount of time a patient's breast must be compressed, thereby increasing the discomfort during the procedure. In other cases, a physician may also decide to use a biopsy device with a smaller aperture and stroke length for various other reasons (e.g., to avoid certain areas).
Current needle sets have adjustable apertures, such as those described in U.S. Pat. No. 6,749,576, the contents of which are incorporated by reference as though fully set forth herein. However, the stroke length is not change, but only “adjusted” by changing the size of the aperture. The distance of travel of the inner cutting cannula remains the same regardless of the size of the aperture. With a smaller aperture, the cutting stroke can be decreased proportionally while still completely severing tissue prolapsing into the smaller aperture.
In some biopsy devices, such as those described in U.S. Pat. No. 7,517,322, the contents of which are incorporated by reference as though fully set forth herein, the stroke length can be manually adjusted to match the adjusted aperture. However, this manual adjustment adds another step to and complicates the tissue biopsy procedure.